Burner unit



Dec. 6, 193s. PgBROSlUS 2,138,998

BURNER UN I T Filed June 24, 1936 2 Sheets-Sheet 2 John P Bros/us, INVENTOR.

Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to improvements in gaseous or vapor fuel burners and more particularly to burners of this type wherein it is desired to premix a predetermined quantity of air and the gaseous or vapor fuel 'prior to delivery to the burner.

The provision of aburner having a positive flame retention nozzle which will substantially maintain a uniform mixture pressure and allow a wide range of turn-down, has become increasingly important since attempts to use previously designed burners to satisfy these requirements have proven unsuccessful. Certain heating operations require an initial high thermal input to effect rapid heating and a relatively small thermal input for maintaining a given temperature condition. Heretofore, this has beeneffected by using burners of suiiicient capacity to provide the maximum thermal requirementsand as the heating chamber approaches a desired temperature the thermal input to the burners is progressively decreased to a required minimum.

When the minimum -thermal output of the burners is in excess of that necessary to maintain the temperature of the heating chamber in equilibrium, certain of the burners are rendered inoperative until a state of equilibrium is reached and this cycle is repeated as required.

This procedure is highly objectionable for several reasons. For example, rendering certain burners in a battery such as alternate burners inoperative causes a correspondingly wider gap between points of heat input, thereby causing a wider temperature dierential between zones of the heating chamber. Again, 4as the thermal input to the burners is decreased there is a corresponding decrease in the mixture pressure at the burner nozzles and for every such decrease there is a corresponding decrease inthe velocity of the gases circulating in the heating chamber. The velocity at which the gases issue from the nozzles determines the shape of the flame since a high velocity ame is relatively long and sharp, whereas a slow velocity ame is short and bushy. A long sharp flame provides more flame surface parallel to the furnace walls than a short stubby flame and the relatively increased flame surface of a long sharp flame radiates more heat to the furnace walls and therefore reduces the ue gas temperature by removing more heat units before the gases pass up the flue. The increased flue gas temperatures, due to low velocity ame, result in a relatively greater heat loss.

Present day burners are limited to their turndown ratio and there is no means of controlling the mixture pressure at the burner nozzles with varying thermal input. This is because a constant port area has definite practical limits of the maximum and minimum pressures, a pressure beyond a predetermined value blowing the mixture from the burner without combustion, and a pressure lower than a predetermined value resulting in fiash back. The mixture pressure affects the efciency of the heating chamber to a considerable degree. For a given thermal input with a relatively low mixture pressure a rather short stubby flame is produced, and with a relatively high mixture pressure a long slender flame results. With a given thermal input a long slender ame will have more effective surface area than a short `stubby flame. Since the emissivity factor of energy delivered to the heating chamber walls is greater with radiated energy than it is with energy delivered by convection of hot gases, it is apparent that the maximum efficiency of the heating chamber will be obtained with a flame having maximum effective surface area.

Furnaces for industrial purposes usually require a considerable temperature range as from 400 F. to 2000 F. dependent upon the particular use of the furnace as for annealing, tempering, heating refractory material and the like. Heretofore, furnaces or sets of furnaces have been required to cover this temperature range or two sets of burners in each furnace since a single burner having a minimum limit of 4009 F. has a maximumlimit of 1000 F. and a burner having a maximum limit of 2000 F. would have a minimum limit of 1000 F.

I am familiar with two port burners which can be individually controlled dependentpn the temperature desired and which employ refractory tunnels as the flame retention means. I am also familiar with ame retention nozzles which do not require a iiame retention tunnel due to a plurality of small orifices at the nozzle port which act to retain the fiame.v However, neither of these burners in itself can exceed the temperature limits previously mentioned.- 4

I have devised a unit which eliminates these disadvantages in providing a plurality of ports individually controlled as to mixture pressure and adapted to a different range of thermal output, but the limits of each range falling within a lower or higher range. This permits of a mixture pres-4 sure for a desired thermal output which, within practical limits, results in eiiicient heating despite a wide range in thermal requirements and to a degree not possible with previous burners with which I am familiar.

It is a primary object of my invention, therefore, to provide a burner for gaseous or vapor fuels which may be efliciently operated over a relatively wide range of thermal requirements.

Another object of my invention is to provide a burner of the above type having a composite wide range turn-down ratio.

Another object of my invention is to provide a burner of the above type which is relatively inexpensive to manufacture and is simple in operation.

Another object of my invention is to provide a burner of the above type having a positive flame retention nozzle.

Another object of my invention is to provide a burner of the above type which can be concurrently operated in a heating chamber with other burners of the same type over all ranges of turndown.

Other objects of my invention, and the invention itself, will become increasingly apparent from a consideration of the following description and drawings, wherein:

Fig. 1 is a sectional view of a heating installation embodying my invention;

Fig. 2 is an enlarged sectional view taken along line 2-2 of Fig. 1;

Fig. 3 is an end elevational view of a neck portion of the unit of Fig. 2 and Figs. 4 and 5 are views similar to Figs. 2 and 3 respectively, of a modification of my invention.

Referring now to the drawings, I have indicated generally at I0 a heating chamber having mounted in a wall II thereof a burner unit genl erally indicated at I2. The wall II may be provided with the usual opening I3 for the reception of the unit I2 which is bolted to the furnace side plates. The unit I2 comprises a relatively large housing divided into smaller'chambers I4 and I5. The chamber I4 comprises walls I6 and I'I coaxially perforated to mount tubular members I8 and I9 respectively. The wall I6 has a sleeve 20 threaded thereinto and the sleeve is also internally threaded to receive a threaded end of tubular member I8, the threads preferably tapering to provide a tight joint as is customary with pipe connections. Although I have illustrated a threaded connection it is understood that any suitable mounting forming a sealed joint may be employed.

Tubular element I8 is mounted in a similar manner in the perforated wall I'I by a threaded sleeve 2|, the elements I8 and I9 being co-axially disposed, the inner wall of element I9 being spaced from the outer wall of element I8 to provide a longitudinally extending passage therebetween. y

An end wall of unit I2 is provided with a generally centrally disposed outwardly extending tubular neck portion 22 within which portions of element I8 and I9 remote from the mounting portions are co-axially projected with the inner walls of neck portion 22 spaced from the' outer wall of element I9 to form a passage therebetween and with the outer end faces of elements I8 and I9 preferably terminating in the plane of `the end face of neck portion 22. l

divergent perforations 25. Tubular element I8 is sometimes referred to as a flame retention nozzle which will support a ame in itself under minimum pressure conditions without the use of a frustro-conical tunnel in the furnace wall as illustrated in Fig. 1 referred to as a flame retention tunnel.

Laterally disposed threaded perforations 26 and 21 form inlet connections for the chambers I4 and I5 respectively from pre-mixing devices indicated generally at 28 and 29. In like manner the sleeve 20 forms an inlet connection from a pre-mixing device 30. The pre-mixing devices 28, 29 and 30 constitute no essential part of my invention and any suitable device well known in the art and adapted to pre-mix air and a cornbustible gas or vapor in a desired ratio and deliver the mixture at a desired pressure, may be used.

It will now be understood that pre-mixed combustible gas or vapor and air at a desired pressure and ratio will be delivered to chamber I4 through inlet 26 and thence to a port indicated at 3| and whose area is determined by the diameters of the inner wall of neck portion 22 and the outer wall of element I9.

In like manner a mixture will be delivered through inlet 21 to chamber I5 and 'to a port 32 formed by the outer wall of element I8 and the inner wall of element I 9, and likewise to a port 33 whose area is dependent upon the diameter of the inner walls of reduced portion 24 of element23.

'I'he areas of ports 3I, 32 and 33 are preferably so designed that the maximum practical and eiiicient range of port 32 includes the minimum range of port 3|, and the maximum range of port 33 includes the minimum range of port 32. Thus, when the heating chamber I0 is being brought up to a desired temperature the thermal input will be supplied through all the ports 3l, 32 and v33 operating simultaneously and as the heating progresses the total thermal input to the heating chamber is reduced by first reducing the thermal inputA through port 3I by regulation of device 28. When the thermal input is reduced to a point approaching the minimum limit of port 3I the device 28 may be cut out of service and the thermal input supplied through port 32 which has a range of lesser thermal input than port 3|, is progressively reduced through regulation of device 29. If the thermal input to heating chamber I0 continues to be greater than desired port 32 is rendered inoperative and port 33 supplied by regulating device 30 becomes the controlling unit. Thus an efcient range of mixing pressures is maintained over a wide fluctuation of thermal input varying from the maximum of the sum of ports 3|, 32 and 33 to the minimum of port 33 alone.

Also any desired combination of ports may be used as required, such as any two or all three ports operating concurrently, excepting that for practical purposes the positive flame retention port 33 should be used in all combinations. Referring to Figs. 4 and 5, I have illustrated a modification of my invention generally similar to that previously described but wherein the vintermediate tubular element I9 is eliminated thereby providing two burner ports rather than three. A plug 40 is inserted in chamber I5 and chamber I5 now supplies pre-mixed combustible vapor or gas to the flame retention nozzle through element I8' and chamber I 4 to a relatively large port 4 I The main difference between this modification and that described in connection with Figs. 1-3 inclusive is that the turn-down ratio of large port Il is less than the composite turn-down ratio of ports 3| and 32,

Although I have shown and described modications or my invention I contemplate that numerous extensions and departures may be made therefrom without departing from the spirit of my `invention and the `scope of the appended claims.

Having thus described my invention what I claim is:

l. The combination with a high temperature furnaceL having an opening formed in the wall thereof, a plurality of devices for pre-mixing air and gaseous or vapor fuel in proportion for substantially complete combustion, manual means for individually controlling the pressure at which the mixture is delivered from each of said devices, of a burner unit having a tubular neck portion insertlble within the furnace opening and having a plurality of individual chambers formed therein, each of said chambers having a tubular extension of diierent cross-sectional area projected within the housing neck portion and disposed coaxially therewith, means connecting each of said chambers with a different pre-mixing device, and flame retention means disposed co-axially within said neck portion and forming part of the central tubular extension.

2. 'I'he combination with a plurality of devices adapted to supply pre-mixed gaseous or vapor fuel and air under individual variably controllable able valve to control the pressure at which the mixture is supplied, of a burner unit having a plurality of separate chambers formed therein, means connecting each of said devices to a difierentchamberwherebythemixturesupplyand pressure to each chamber may be selectively controlled by the valves, each of said chambers having an outlet conduit extending in concentric relation to a common opening in the unit wall,

and a ame retention means mounted in the unit necting each of said devices t`o a diierent chamber whereby the mixture supply and pressure to each chamber may be selectively controlled by thev valves, each of said chambers having an outlet conduit extending to a common opening in the unit wall, and a flame retention means mounted in the unit forming part of one conduit and adapted to be selectively operated with the other conduits.

5. The method of providing a flame of mairimum heating value over a wide vthermal output and temperature range which includes supplying pre-mixed gaseous or vapor fuel and air, selectively from a plurality of independent sources to a common combustion zone, arranging the mixture to enter the combustion -zone in successive envelopes about a central mixture, and combining the central mixture with selective mixtures from the other sources under variably controllable pressure to provide a long slender llame.

6. The combination with a plurality of devices adapted to' supply pre-mixed gaseous or vapor fuel andv air, each device having a manually operable valve to control the pressure at which the `mixture is supplied, o1' a burner unit having a.

plurality of conduits terminating in concentric relation at an opening provided in the wall of the burner unit, said unit being adapted to be associated with a furnace to supply fuel mixture thereto, each conduit being connected to a diiler- 

